(1) Field of the Invention
The present invention relates to a refrigeration system used in an automotive air conditioner using a gas harmful to a human body as refrigerant.
(2) Description of the Related Art
A typical refrigeration system used in automotive air conditioners comprises a compressor that compresses refrigerant circulating through a refrigeration cycle, a condenser that condenses the compressed refrigerant, a receiver/dryer that separates the condensed refrigerant into a gas and a liquid while temporarily storing the refrigerant circulating through the refrigeration cycle, an expansion device that throttles and expands liquid refrigerant obtained by gas/liquid separation, and an evaporator that evaporates the expanded refrigerant to return the same to the compressor (see e.g. Japanese Unexamined Patent Publication (Kokai) No. 2002-147898 (Paragraph number [0011], and FIG. 1)).
Although in the refrigeration cycle for an automotive air conditioner, a CFC substitute (HFC-134a) has been used as refrigerant, the use of refrigerant with a small global warming potential has come to be demanded in view of global warming. As such a refrigerant; there are considered e.g. carbon dioxide, HFC-152a, butane, and propane.
However, for example, when carbon dioxide is used as refrigerant for an automotive air conditioner, in case an evaporator disposed in a space leading to a vehicle compartment or piping disposed in the vehicle compartment is broken or cracked due to aging to cause release of refrigerant into the vehicle compartment, there is a danger of suffocation of vehicle occupants due to oxygen deficiency, whereas when an inflammable gas, such as HFC-152a, is used as refrigerant, in case of the above-mentioned event, there is a possibility of the inflammable gas catching a fire to set the vehicle on fire, causing serious influence on the vehicle occupants.